JP2951456B2 - Coriolis mass flowmeter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Coriolis mass flowmeter having an improved S / N ratio.

[0002]

2. Description of the Related Art FIG. 16 is an explanatory view of the configuration of a conventional example generally used in the prior art, which is used in a Coriolis mass flowmeter. For example, US Pat. No. 4,491,025, entitled "PARALLEL" PATH CORIOLIS MASS FLOW RATE METE
R ", filed November 3, 1982, and filed on January 1, 1985. In the figure, reference numeral 1 denotes a U-shaped measuring pipe having both ends attached to a pipe A. Reference numeral 2 denotes a mounting flange of the measuring pipe 1 to the pipe A. Reference numeral 3 denotes a vibrator provided at the tip of the U-shaped measuring tube 1. Reference numerals 4 and 5 denote displacement detection sensors provided on both sides of the measuring tube 1, respectively.

In the above configuration, a measurement fluid is caused to flow through the measurement tube 1, and the vibrator 3 is driven. Assuming that the angular velocity in the vibration direction of the vibrator 3 is “ω” and the flow velocity of the measurement fluid is “V” (hereinafter, the symbol surrounded by “” indicates a vector quantity), Fc = −2 m “ω” × “V” The mass flow rate can be measured by measuring the amplitude of the vibration in which the Coriolis force acts and which is proportional to the Coriolis force. However, in general, the amplitude of the vibration proportional to the Coriolis force is much smaller than the amplitude of the vibration due to the excitation, and it is difficult to directly detect the amplitude of the vibration proportional to the Coriolis force.

When the vibration direction is divided into α and β by vibrating the vibrator 3 when viewed from the Z direction in FIG. 16, depending on the direction of the flow velocity “V”, FIGS. As shown, since the directions of the Coriolis force are different, the phases are reversed, and the measuring tube 1 vibrates while being twisted. The displacement is detected by the displacement detection sensors 4 and 5, for example, magnetic sensors, and the phase difference between the displacements of the displacement detection sensors 4 and 5 is (amplitude of vibration proportional to Coriolis force) / (amplitude of vibration due to excitation) , The mass flow rate can be determined. Since the phase difference can be measured as the time difference Δt at which the waveform crosses zero, the Coriolis force can be measured as a result.

FIG. 19 is an explanatory view of the structure of another conventional example generally used. In this conventional example, in order to further reduce noise and increase the signal, the measuring tube 1 is
The two-tube system is used to cancel noise.

[0006]

However, in such an apparatus, the displacement caused by the Coriolis force is as small as about 1/1000 compared to the displacement caused by driving. As a result, the time difference Δt due to the Coriolis force is also small, and the resolution is poor. The present invention solves this problem. An object of the present invention is to provide a Coriolis mass flowmeter having an improved S / N ratio with respect to a drive signal by directly detecting a displacement caused by a Coriolis force.

[0007]

In order to achieve this object, the present invention provides a method of flowing a measuring fluid into a vibrating measuring tube, and deforming the measuring tube by a Coriolis force generated by the flow and the angular vibration of the measuring tube. A Coriolis mass flowmeter provided in the measurement tube, the Coriolis mass flowmeter comprising an additional vibrator having sensitivity to Coriolis force and low sensitivity to driving vibration. It is composed.

[0008]

In the above arrangement, the measuring fluid is caused to flow through the measuring tube, and the measuring device is excited by the driving device. An additional vibrator that has sensitivity to Coriolis force and low sensitivity to drive vibration is provided.By measuring the vibration displacement of the additional vibrator, the displacement due to the Coriolis force can be directly measured. Since a large detection can be performed, a Coriolis mass flowmeter with an improved S / N ratio can be obtained. Hereinafter, a detailed description will be given based on embodiments.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram of a main portion of an embodiment of the present invention. In the figure, the configuration of the same symbol as FIG. 16 represents the same function. Hereinafter, only differences from FIG. 16 will be described. 1
1 is a linear measuring tube, and 12 is a housing. 13
Is a drive unit that excites the measurement tube 11 in a direction perpendicular to the axis of the measurement tube 11. The drive unit 13 includes a coil 14 attached to the housing 12 and a core 15 attached to the measurement tube 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference numeral 16 denotes a drive displacement detection sensor for checking the operation of a drive unit 13. The drive displacement detection sensor 16 includes a magnet 17 and a core 18. 19 is an additional oscillator. As shown in FIG. 3, the additional oscillator 19 includes an additional oscillator fixing portion 21 and a T-shaped beam portion 24 including a vertical beam 22 and a horizontal beam 23. In this case, a pair of beams 24 are attached, but need not necessarily be a pair.
A piezoelectric element 25 measures the vibration of the additional vibrator 19. The additional vibrator 19 has sensitivity to Coriolis force and low sensitivity to drive vibration. That is, the vertical beam 22 is short and the horizontal beam 23 is long.

In the above configuration, the measurement fluid is caused to flow through the measurement tube 11, and the measurement tube is excited by the drive unit 13. Since the additional vibrator 19 having sensitivity to Coriolis force and low sensitivity to driving vibration is provided, by measuring the vibration displacement of the additional vibrator, the displacement due to the Coriolis force is directly measured. Can be detected largely, so that a Coriolis mass flowmeter with an improved S / N ratio can be obtained.

That is, FIGS. 4A, 4B, 4C, and 4D
2 shows a state of vibration of the measuring tube 11 when the measuring fluid is not flowing through the measuring tube 11. FIG. 5 (a) (b) (c)
(D) shows a state of vibration of the measurement tube 11 when a measurement fluid is flowing through the measurement tube 11.

Since the Coriolis force has a rotationally symmetric distribution in the upstream and downstream directions with the center of the measuring tube 11 as the origin, FIG.
(B) Vibration shown in (c) and (d). With this vibration, the additional vibrator 19 rotationally vibrates. Since the amplitude of the rotational vibration is proportional to the Coriolis force, the Coriolis force is measured by measuring the amplitude. Coriolis force is measured by measuring tube 11
Is proportional to the mass flow through That is, the additional vibrator 1
By measuring the rotation amplitude of No. 9, the mass flow rate can be measured.

As a result, (1) Coriolis force can be detected with high sensitivity. Therefore,
The SN ratio of the detection signal can be improved. (2) Coriolis force is proportional to drive displacement. Since the detection of the Coriolis force can be obtained with high sensitivity, the drive displacement can be made smaller than before. Therefore, the possibility of the measurement tube 11 rupture due to stress corrosion due to vibration is reduced.

FIG. 7 is an explanatory diagram of a main part configuration of another embodiment of the present invention. In this embodiment, the additional vibrator 19 is constituted by a beam 24 on a plate on an axis perpendicular to the measuring tube 11 without a plane of driving vibration. FIG. 8 is an explanatory view of a main part configuration of another embodiment of the present invention. In this embodiment,
The direction of the additional vibrator 19 shown in FIG.

FIG. 9 is an explanatory view of a main part of another embodiment of the present invention. FIG. 10 is a side view of FIG. 9, and FIG. 11 is a detailed explanatory view of the torsional displacement measuring device of FIG. In this embodiment,
The additional oscillator 19 is constituted by a torsion oscillator composed of a shaft 31 orthogonal to the plane of the driving vibration, a large mass 32 at the tip thereof, and a torsional displacement measuring device 33.

As shown in FIG. 11, the torsion displacement measuring device 33 includes a piezoelectric element 34, a connecting portion 35, and a connecting screw 36. The piezoelectric element 34 is fixed to the measuring tube 11 by a coupling portion 35 and a coupling screw 36, and when twisted, generates a voltage proportional to the twist. FIG. 12 is an explanatory diagram of a main part configuration of another embodiment of the present invention. In the present embodiment, a sliding mode detection type is used as the piezoelectric element 25.

FIG. 13 is an explanatory diagram of a main part configuration of another embodiment of the present invention. In the present embodiment, U
FIG. 14, which uses a tube, is an explanatory view of a main part configuration of another embodiment of the present invention. In this embodiment, an S-shaped tube is used as the measuring tube 11. FIG. 15 is an explanatory view of a main part configuration of another embodiment of the present invention. In the present embodiment, a parallel tube is used as the measurement tube 11. In the above-described embodiment, the case where the piezoelectric element 25 is used as the vibration detection sensor has been described.
The present invention is not limited to this, and may be, for example, an optical sensor, an electrodynamic sensor, or an electrostatic sensor. Further, the driving unit 13 may use a piezoelectric element instead of the electromagnetic coil. Further, the detection of the drive displacement detection sensor 16 may be an optical sensor other than the electrodynamic sensor or an electrostatic sensor. Alternatively, the detection may be performed by the piezoelectric element 25 of the additional vibrator 19.

[0018]

As described above, the present invention relates to a Coriolis mass flowmeter which deforms and vibrates a measuring tube by flowing a measuring fluid into a vibrating measuring tube and causing Coriolis force generated by the flow and the angular vibration of the measuring tube. A Coriolis mass flowmeter, comprising an additional vibrator provided on the measurement tube and having sensitivity to Coriolis force and low sensitivity to driving vibration.

As a result, (1) Coriolis force can be detected with high sensitivity. Therefore,
The SN ratio of the detection signal can be improved. (2) Coriolis force is proportional to drive displacement. Since the detection of the Coriolis force can be obtained with high sensitivity, the drive displacement can be made smaller than before. Therefore, the risk of pipe rupture due to stress corrosion due to vibration is reduced.

Therefore, according to the present invention, a Coriolis mass flowmeter with an improved S / N ratio can be realized.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a main part configuration of an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a detailed explanatory view of a main part of FIG. 1;

FIG. 4 is an operation explanatory diagram of FIG. 1;

FIG. 5 is an operation explanatory diagram of FIG. 1;

FIG. 6 is an operation explanatory diagram of FIG. 1;

FIG. 7 is an explanatory view of a main part configuration of another embodiment of the present invention.

FIG. 8 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 9 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 10 is a side view of FIG. 9;

11 is a detailed explanatory diagram of a main part of FIG. 9;

FIG. 12 is an explanatory view of a main part configuration of another embodiment of the present invention.

FIG. 13 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 14 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 15 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 16 is an explanatory diagram of a configuration of a conventional example generally used in the related art.

FIG. 17 is an operation explanatory diagram of FIG. 16;

FIG. 18 is an operation explanatory diagram of FIG. 16;

FIG. 19 is an explanatory view of the configuration of another conventional example generally used in the prior art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Measuring tube 12 ... Housing 13 ... Vibration part 14 ... Coil 15 ... Core 16 ... Drive displacement detection sensor 17 ... Magnet 18 ... Core 19 ... Additional oscillator 21 ... Additional oscillator fixing part 22 ... Vertical beam 23 ... Horizontal beam 24 ... Beam 25 Piezoelectric element 31 Shaft 32 Mass 33 Torsional displacement measuring device 34 Piezoelectric element 35 Coupling portion 36 Coupling screw

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenichi Kuromori 2-9-32 Nakamachi, Musashino-shi, Tokyo Examiner, Yokogawa Electric Co., Ltd. Masahiro Etsuka (56) References JP-A-2-206722 (JP, A) JP-A-2-213726 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01F 1/84

Claims (1)

(57) [Claims] 1. A Coriolis mass flowmeter for flowing a measuring fluid through a vibrating measuring tube and deforming and vibrating the measuring tube by the Coriolis force generated by the flow and the angular vibration of the measuring tube. A Coriolis mass flowmeter comprising an additional vibrator configured to be sensitive to driving vibration and low in sensitivity to driving vibration.